Sound reproducing system



March 6, 1934. G. B. scHElBELL SOUND REPRODUCING SYSTEM Filed March 12, 1931 3 Sheets-Sheet 1 LIGHT I Amour/5@ I F/ 759,0'

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March 6, 1934. G, B SCHE|BELL 1,950,011

SOUND REPRODUC ING SYSTEM Filed March 12, 1931 3 Sheets-Sheet 2 IIIHIIHIH IH'IIIHHIIIIII INVENTOR. j Qjow @mmm/v csf/fzeiaf,

ATTORNEY March 6,1934. G, B. scHElBl-:LL

SOUND REPRODUCING SYSTEM Filed March 12. 1931 3 Sheets-Sheet 3 I N VEN TOR Qfcow @fw/mw CSi/gem,

B Y y l A A TTORN Y Patented Mar. 6, 1934 UNITED STATES PATENT OFFICE SOUND REPRDUCHNG SYSTEM Gordon Brown Scheibell, Newark, N. J., assignor to Wired Radio, Inc., New York, N. Y., a cor- My invention relates broadly to sound recording and reproducing and more particularly to a system for recording and reproducing sound on lm.

One of the objects of my invention is tc provide a system for recording and reproducing sound by frequency segregation in which the quality of reproduced sound is greatly improved.

Another object of my invention is to provide a system for recording and reproducing sound in which thel sound programs which are recorded are divided into a multiplicity of diiierent channels along the iilm, each channel being eiiective over a particular range of audio frequencies, the reproducing apparatus being operative over a corresponding number of sound channels for the reproduction of sound over the different ireH quency ranges from the different channels with great fidelity.

Still another object of my invention is to provide a method of recording and reproducing sound on iilm which consists in dividing the total irequency range of the sound into a multiplicity of separate channels, each of which is responsive to a limited audio frequency band Within the total frequency band for efliciently integrating the operation of the circuits for the reproduction of sound at high quality. 1

A further object of my invention is to provide a system of sound recording and reproduction in which the ampliiication circuits in the sound system are efficiently constructed for passing audio frequencies within a particular audio irequency band making up the entire audio irequency range over which the sound recording and reproducing system is operative.

Other and further objects of my invention reside in the arrangement of circuits and apparatus for the multiple channel sound recording and reproducing system of my invention as set forth more fully in the specification hereinafter iollowing by reference to the accompanying dra-W- ings, in which:

Figure 1 diagrammatically illustrates a sound recording system employing the principles of my invention; Fig. 2 schematically shows the operation of the successive sound recording cir cuits for the sound film system of my invention; Fig. 3 illustrates a fragmentary portion oi a sound nlm bearing a multiplicity of sound recn ords thereon according to the system of my invention; Fig. 4 is a perspective view of a sound reproducing apparatus employed in the system of my invention; and Fig. 5 diagrammatically illustrates the arrangement of sound reproducing 1931, Serial No. 522,094

system constructed in accordance with the principles of my invention.

My invention is directed to a system for increasing the eiiiciency oi reproduction of sound in a system employing a iilm record. In recording and reproducing acoustical vibrations, I provide a plurality of sound pick-up circuits which connect through separate ampliers and independent sound iilter circuits. The separate sound channels control independent light valves aligned with different longitudinal tracks along the nlm. The independent circuits are each responsive to particular range of audio frequency Within the total band of audio frequencies. 1Eilter circuits are arranged in each of the sound channels for rendering such channels responsive to frequencies lying Within the range oi frequencies to which the individual channels are selective. Inasmuch as each recording circuit is eiiicient over a limited frequency range, a high degree of efnciency is obtained over the entire frequency scale in the recording system. In the reproducer, the reproducing circuits are divided into channels which are controlled by the individual sound records for the eicient reproduction of sound. The variable frequency ranges of the diierent acoustical vibrations are more faithfully reproduced in the system or" my invention due to the eiiicient characteristics of the recording and reproducing circuits designed for particular ranges of audio frequencies.

Referring to the drawings in more detail, reference character 1 designates a photosensitive film on which the multiple sound channels are recorded. The film is carried by reels 2 and 3 which are driven by motor 4 operated from the source 5 through switches 6. The separate recording lamps for each of the several sound channels are shown at 7, 8 and 9, each adapted to direct light rays upon the photosensitive nlm 1 through the independent light valves 10, 1l and 12 which are longitudinally displaced from each other along the iilm as shown. These light valves are devices for controlling the intensity oi a light beam in accordance With electrical energy and may be of any conventional type Well known in the art of recording sound on iilm, The light valves are actuated by the separate sound control circuits connected with microphones lll, 15 and 16 which separately control the independent amplifiers 1'?, 19 and 21. The ampliiiers independently connect tc separate lter circuits 18, 2o and 22 which I have designated lilters A, B and C, the outputs of which lead to the separate light valves 10, l1 and 12. The iilters 18, 2o and 22 operate over predetermined audio frequency ranges within the entire audio frequency range of the sound recording system and control light valves 10, 11 and 12 which control the amounts of light from sources 7, 8 and 9 to be recorded upon the photosensitive film 1, The light source 7 is energized from battery 23, the light source 8 is energized from battery 24 and the light source 9 receives its energy from battery 25. Any suitable source of energy may be employed in lieu of the batteries indicated in the schematic diagram.

The filters 18, and 22 each comprise a network adapted to substantially attenuate variable currents at all frequencies other than those lying Within a predetermined band of frequencies. Such networks are known as band pass filters and are well known in the art of electrical communication. In Fig. 2 the response characteristics of the several filter circuits 18, 20 and 22 have been graphically represented. The filter A at 18 comprises a network having co-nstants such that currents at frequencies below the upper cut-off frequency f3 and above the lower cutoff frequency f1 will be transmitted therethrough, while currents at frequencies lying outside of the frequency range ya-fi will be substantially attenuated as indicated by curve 26. The upper cut-off frequency f3 is approximately 180 cycles while the lower cut-ofi frequency f1 is approximately 50 cycles.

The filter B at 20 comprises a network having constants such that currents at frequencies below the upper cut-off frequency f5 and above the lower cut-01T frequency f2 will be transmitted therethrough, while currents lying outside of the frequency range fri-f2 will be substantially at- Ytenuated as indicated by curve 27. The upper cut-off frequency f5 is approximately 1,000 cycles while the lower cut-off frequency f2 is approximately 180 cycles.

The filter C at 22 comprises a network having constants such that currents at frequencies below the upper cut-off frequency fs and above the lower cut-off frequency fi will be transmitted therethrough, while currents at frequencies outside of the frequency range frif4 will be substantially attenuated as indicated by curve 28. The upper cut-off frequency f6 is approximately 8,000 cycles, while the lower cut-off frequency f4 is approximately 1,000 cycles. It will be noted that, according to my invention, the frequency range represented by curve 27 is more than twice as great as the frequency range represented by curve 26, while the frequency range represented by the curve 28 is more than twice as great as the frequency range represented by the curve 27. Consequently, the numerical difference of any two of the frequency ranges will be greater than the range of the smaller of the two frequency ranges. Such a condition provides a relatively narrower frequency range for the filter circuits handling the lower frequencies thereby permitting more efficient filter design and correspondingly greater 4efficiency in the system.

bers of filters can be used for different arrangements of frequency segregation without departing from the scope of my invention.

Fig. 3 represents the sound film 1 as produced by the circuit arrangement of Fig. 1 showing the three different sound tracks 29, 30 and 31, respectively, representative of the three filters A, B and C.

The apparatus for reproducing the multiple sound channel film thus recorded is shown in Fig. 4 wherein the frame support 32 provides a mounting means for the projecting shafts 33 and 33a on which there is rotatably mounted the reels 35 and 43. Pulley member 34 provides means for positively driving the reel 35 through belts 36 as shown. Belt 36 is driven from driving pulley 37 operated by motor 38. The motor 38 also drives belt 39 imparting rotary motion to sprocket drive 41 journaled upon shaft 40 for feeding film 1 with respect to the reels 35 and 43. Idler rollers 46 and 46a provide guides for the film 1. Film 1 is provided with a multiplicity of sound channels thereon as designated at 29, 30 and 31 which register with separate light slits 8l, 82 and 83 in the independent housings shown at 51, 52 and 53. The separate housings are supported by appropriate brackets 51a, 52a and 53a extending from the frame 32 and are longitudinally displaced with respect to each other along film 1 as shown. Aligned with the housings 51. 52 and 53 on the opposite side of film 1, I provide lamp housings each containing a light source designated at 61, 62 and 63. The several light sources are individually aligned with their respective sound track on the film 1 and serve to direct rays of light through the sound tracks simultaneously and through the apertures 81, 82 and 83 upon the photoelectric cells 71, 72 and 73 as shown. The photoelectric cells are therefore simultaneously activated by varying light rays under control of the different sound tracks each of which contain sound frequencies of different frequency ranges forming part of the same sound program.

In Fig. 5, I have illustrated the circuit arrangement for the several light and photocell circuits. The lamps 61, 62 and 63 are shown energized from source 56 through the switch system 57. The photocell 71 is connected in the input circuit of the transformer coupled audio frequency amplifier 58, the circuits of which are responsive to the particular range of audio frequencies which will be reproduced under control of the sound channel 29 (Fig. 3). The output circuit of the amplifier 58 terminates in a. potentiometer 64 over which slidable contact 67 is adjustable and which connects to a translating device, or loud speaker 70. The photoelectrlc 130 cell 72 which is activated by lamp 62 is connected in the input circuit of the transformer coupled amplifier 59, the output circuit of which includes potentiometer 65 having sliding contact 68 thereon which connects to the translating 135 device 49. The photoelectric cell 73 connects through transformer coupled amplifier to the output potentiometer 66 along which contact 69 is adjustable. Contact 69 connects to the translating device 47. It will be understood that am- 140 plifiers 58, 59 and 60 and translating devices 70,

49 and 47 are adjusted for the efficient amplification of audio frequency energy over the range covered by the sound records 47, 48 and 49, respectively. The amounts of energy Within each 145 audio frequency range may be selectively controlled by adjusting the position of sliding contacts 67, 68 and 69 on the potentiometers 64, and 66, respectively for producing balancing and other effects in the translating devices or 150 sound reproducers 70, 49 and 47, as, for example, in Fig. 5 where it will be seen that the potentiometer 68 is set at a point different from the potentiometers 67 and 69 so that the frequencies translated by reproducer 49 will be at a volume level different than those translated by reproducers 70 and 47. The film 1 is driven by means of motor 38 connected with reel 35 and energized from suitable source 54 through switch 55.

The unique design of the independent sound channels employed in the recording and reproducing process permits the composite operation of the several channels for securing operation of the sound reproduction system with accurate tone quality over the entire range of audio frequencies for which the system is designed to operate.

While I have described my invention in one of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. The method of reproducing sound comprising, individually acoustically selecting a plurality of different sound frequencies for conversion into electrical energy at corresponding frequencies, electrically selecting said electrical frequencies within predetermined frequency bands, utilizing a common moving recording element for making individual records of said electrical frequencies all displaced from each other along the path of movement of said element, individually controlling different electrical circuits with said individual records, and individually controlling acoustical reproducing devices with said individual circuits for simultaneous reproduction of said original acoustical frequencies.

2. The method of reproducing sound in accordance with claim 1 in which said predetermined frequency bands are of progressively increased extent.

3. The method of reproducing sound comprising, individually acoustically selecting a plurality of different sound frequencies for conversion into electrical energy at corresponding frequencies, electrically selecting and amplifying said frequencies within predetermined frequency bands of progressively increased extent, making individual records of said electrical frequencies, upon a common recording element in a manner such that all of said records are displaced from each other along the path of movement of said element in a reproduction process, moving said element and simultaneously individually con- ,trolling different electrical circuits with said individual records, and individually controlling acoustical reproducing devices with said individual circuits for simultaneous reproduction of said original frequencies.

4. In a system for the reproduction of sound comprising, a plurality of translating devices each designed to operate most efficiently substantially within a certain range of frequencies for picking up acoustical vibrations in a substantially restricted portion of the audio frequency range, a plurality of individual amplifiers respectively connected with said translating devices for converting said acoustical vibrations into amplified electrical frequencies, a plurality of electrical filters respectively connected with said amplifiers and designed to select and pass electrical frequencies only within predetermined and mutually exclusive frequency bands and each adapted to cut off frequencies appearing in its respective amplifier which overlap into the frequency range of another filter, and a plurality of light valves individually designed to operate at maximum efiiciency within the restricted frequency bands of said filters, each of said light valves receiving said electrical frequencies directly from its respective filter, the method of, simultaneously directing light through said light valves to a single photosensitive film at positions longitudinally displaced along said film to produce a plurality of individual photographic records each bearing frequencies within the frequency band of one of said filters, subsequently directing light simultaneously through said individual photographic records to individually produce electrical frequencies within frequency bands each band of which corresponds to the frequency band of one of said electrical filters, and individually converting said reproduced bands of electrical frequencies into corresponding acoustical vibrations of controlled amplitudes for compositely reproducing the original audio frequency range.

GORDON BROWN SCHEIBELL. 

